Heretofore, tank fittings have been secured to the tanks by welding in order to insure a leak-proof connection. The tanks and associated fittings were usually constructed of metal, such as steel, which made them amenable to welding. With the advent of plastics, particularly high density, cross-linked polyethylene, many tanks are being constructed of plastic since plastic provides a material more durable and less expensive than metal and not subject to corrosion when the tanks are being employed to store acids and alkaline solutions; however, cross-linked polyethylene is not weldable or fusible; accordingly, fittings to be used with the plastic tank have to be mechanically connected to the tank in such a manner so as to provide a leak-proof connection.
After considerable research and experimentation, the tank fitting of the present invention has been devised which can be mechanically connected to a plastic tank to thereby provide a leak-proof connection. The fitting of the present invention comprises, essentially, a three flanged polyolefin fitting wherein two of the flanges are integrally connected to a pipe adapted to extend through the tank wall. The end of the pipe within the tank is provided with a threaded portion to which a siphon drain is connectable. Two flanges are positioned at the opposite end of the pipe with one flange being on the end of the pipe and the other flange being positioned on the pipe between the first-mentioned flange and threaded portion. The third flange consists of a flange connector slidably mounted on the portion of the pipe within the tank and having bolts extending axially from the third flange through the tank wall and second flange and secured thereto by suitable nuts. Compressible gaskets are provided on the inner faces of the second and third flanges with the tank wall extending therebetween.